Doors and windows are typically used for one or more of the following purposes: to open and close an entrance or opening, to separate an area, to restrict access and to provide visual privacy.
In order for a door or window to perform its intended functions effectively, it is desirable that the door or window be easily operable and fully openable. It is also desirable that the door or window takes up a small footprint, especially when installed in an area with space constraints.